The vast majority of Apache HTTP Server instances run on a Linux distribution,^[5] but current versions also run on Microsoft Windows,^[6] OpenVMS,^[7] and a wide variety of Unix-like systems. Past versions also ran on NetWare, OS/2 and other operating systems,^[8] including ports to mainframes.^[9]


Originally based on the NCSA HTTPd server, development of Apache began in early 1995 after work on the NCSA code stalled.^[10] Apache played a key role in the initial growth of the World Wide Web,^[11] quickly overtaking NCSA HTTPd as the dominant HTTP server. In 2009, it became the first web server software to serve more than 100 million websites.^[12]


As of March 2022, Netcraft estimated that Apache served 23.04% of the million busiest websites, while Nginx served 22.01%; Cloudflare at 19.53% and Microsoft Internet Information Services at 5.78% rounded out the top four. For some of Netcraft's other stats, Nginx is ahead of Apache.^[13] According to W3Techs' review of all web sites, in June 2022 Apache was ranked second at 31.4% and Nginx first at 33.6%, with Cloudflare Server third at 21.6%.^[14]